如何在 ubuntu 16.04 中从 php 7.0 升级到 php 7.1？
如果我这样做，php -v我会收到此消息：
PHP 7.0.8-0ubuntu0.16.04.3 (cli) ( NTS )
Copyright (c) 1997-2016 The PHP Group
Zend Engine v3.0.0, Copyright (c) 1998-2016 Zend Technologies
with Zend OPcache v7.0.8-0ubuntu0.16.04.3, Copyright (c) 1999-2016, by Zend Technologies